Apparatus and method for chilling cryo-ablation coolant and resulting cryo-ablation system

ABSTRACT

Apparatus and methods for cooling liquid coolant, such as nitrous oxide, to be delivered to a cryo-ablation device such as a balloon catheter. A hose or conduit in fluid communication with the ablation device includes an outer member and inner tubes. A first inner tube disposed within a lumen of the outer member carries liquid coolant to the ablation device. Another inner tube also disposed within the lumen carries liquid coolant and terminates within the lumen such that gaseous coolant derived from liquid coolant flowing through the second inner tube flows within the lumen to cool or chill the first inner tube and liquid coolant carried by the first inner tube to the ablation device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/432,465, filed on Apr. 29, 2009, now U.S. Pat. No. 9,028,445, whichclaims priority from the earlier filed U.S. Provisional Application No.61/052,598, filed May 12, 2008, the entirety of which are herebyincorporated into this application.

FIELD OF THE INVENTION

The present inventions relate to cryo-ablation devices, systems andassociated methods.

BACKGROUND

Cardiac arrhythmias are a significant health problem, and atrialfibrillation is a common cardiac arrhythmia. Although atrial arrhythmiasmay not be as fatal as frequently as ventricular arrhythmias, atrialarrhythmias increase risk factors for other conditions such asembolisms. Further, atrial arrhythmias can contribute to the onset ofventricular arrhythmia.

It is believed that cardiac electrical impulses normally start in asinoatrial (SA) node, spread through the atria, and progress through theatrial-ventricular (AV) node to the ventricles to complete a heartbeat.Atrial fibrillation is an irregular heart rhythm that originates inabnormal cells in the atria, the upper two chambers of the heart. Musclefibers in the pulmonary veins, in particular, can be sources ofdisruptive re-entrant electrical impulses.

One known method of treating atrial fibrillation is by use of medicationthat is intended to maintain a normal sinus rate and/or decreaseventricular response rates. It is also known to use implant devices suchas atrial pacemakers to treat these conditions. Other known methods anddevices have been developed for creating therapeutic lesions, e.g., byopen-heart or minimally-invasive surgical methods, in the myocardialtissue to block sources of unwanted electrical impulses that arebelieved to be the source of atrial fibrillation. In this context,ablation has come to mean the deactivation, or removal of function,rather than the removal of the tissue, per se. A number of energysources may be used for creating these “blocking” lesions that may betransmural and extend across the entire heart wall to isolate theunwanted sources of activation from the rest of the excitable tissue inthe heart.

Formation of lesions may be performed using both endocardial andepicardial devices and procedures. Endocardial procedures are performedfrom within the heart. Since the endocardium primarily controlsmyocardial functions, there are inherent advantages to generatinglesions by applying an energy source to endocardial surfaces. One knownmanner of applying energy for this purpose is to utilize radio frequency(RF) catheters, which ablate tissue by heating it over about 50° C.Other devices and procedures involve cryo-ablation. Cryo-ablationdevices ablate tissue by freezing the tissue to permanently destroy itsfunction. Examples of known lesion formation devices, includingcryogenic balloon catheters for use in endocardial ablation and theiroperation are described in U.S. Patent Application Publication No.20060084962, U.S. Pat. Nos. 6,027,499; 6,468,297; 7,025,762; 7,081,112and 7,150,745 and Williams, et al, “Alternative Energy Sources forSurgical Atrial Ablation”, J. Card. Surgery, 2004; 19:201-206, thecontents of which are incorporated herein by reference as though setforth in full.

The effectiveness of cryogenic balloon catheters depends on variousfactors including, for example, successfully delivering high qualitycryogenic coolant or refrigerant (generally referred to as “coolant”)from a pump, pressure reservoir or other refrigerant source and to thetarget site or tissue to be treated. Certain known cryogenic ballooncatheters operate as a closed-loop fluid system. Coolant is fed to thecatheter at a high pressure, and cryogenic cooling results fromevaporation of the coolant resulting from a pressure drop as thecryogenic fluid is sprayed into the interior of a balloon at thecatheter tip. The quality of the coolant, e.g., the relative proportionof the coolant, which may be in liquid state, is determined by the localpressure and temperature of the coolant relative to the vapor saturationline for the coolant. For example, 100% saturation may be preferred.

Ideally, the coolant is delivered to the catheter tip at a sufficientlylow temperature and a sufficiently high pressure such that thecombination of the low temperature and high pressure is above the vaporsaturation line for the coolant. However, during use, the pressure ofthe liquid coolant drops and the temperature of the coolant may increaseas the liquid flows through a coolant supply line or hose and thecatheter. The resulting pressure drops and higher temperaturesnegatively impact the quality of the cryogenic coolant that is deliveredto the tip of the cryogenic catheter, increasing fluid resistance, whichreduces the rate at which liquid coolant is provided to the cathetertip. This diminishes the cryogenic effect of the coolant and the qualityof lesions that are formed thereby. For example, if the temperature ofliquid nitrous oxide is increased by a certain degree, gas bubbles willform within the nitrous oxide coolant. These bubbles increase fluidresistance of the coolant as the coolant flows through a small diametersupply tube or conduit, thus reducing the rate at which liquid nitrousoxide coolant can be provided to the tip of the catheter to performcryo-ablation.

One attempt to address these issues is to maintain the liquid coolant inthe supply path adequately above the saturation line by increasing thelocal pressure, lowering the local temperature, or both. For thispurpose, it is known to utilize a cryogenic supply console, which istypically located near the clinician and is used to chill the coolantthat is supplied to the catheter. These supply consoles are typicallylarge components and incorporate a compressor or a heatexchanger/chiller to provide coolant at desired pressures andtemperatures. For example, one known supply console has a largemechanical compressor that is used to liquefy gas refrigerant at a highpressure, and another known supply console has a heat exchanger/chillerto liquefy the refrigerant vapor and deliver it at a low temperature.Such large supply consoles may initially provide coolant having desiredcharacteristics, but the required console equipment is bulky and of sucha size that it is not desirable to have them in operating environments.Other difficulties arise from placing such large consoles at a distancefrom operating environments due to associated warming of the liquidcoolant, increased fluid resistance, and decreased coolant flow to thetip of the catheter.

SUMMARY

According to one embodiment, an apparatus for cooling a coolant to bedelivered to a cryo-ablation device includes an outer member having aproximal end and a distal end and defining a lumen, a first inner tubeand a second inner tube. The first inner tube is disposed within thelumen and configured to carry coolant to the cryo-ablation device. Thesecond inner tube is disposed within the lumen and configured to carryliquid coolant. A distal end of the second inner tube terminates withinthe outer member lumen such that gaseous coolant formed by or derivedfrom evaporation of the coolant flowing through the second inner tubeflows within the lumen to cool the first inner tube and liquid coolantcarried by the first inner tube.

Another alternative embodiment is directed to a cryo-ablation systemthat includes a cryo-ablation device configured to cryogenically ablatetissue, and a hose or conduit that is in fluid communication with thecryo-ablation device and configured to cool a coolant, such as a liquidcoolant, to be delivered to a cryo-ablation device for tissue ablation.The hose or conduit comprises an outer member having a proximal end anda distal end and defining a lumen, a first inner tube and a second innertube. The first inner tube is disposed within the lumen and configuredto carry coolant to the cryo-ablation device. The second inner tube isdisposed within the lumen and configured to carry liquid coolant. Adistal end of the second inner tube terminates within the outer memberlumen such that gaseous coolant formed by or derived from evaporation ofthe coolant flowing through the second inner tube flows within the lumento cool the first inner tube and liquid coolant carried by the firstinner tube.

Another embodiment is directed to a method of cooling liquid coolant tobe delivered to a cryo-ablation device. The method comprises deliveringliquid coolant through a first inner tube extending through a lumendefined by an outer member; delivering liquid coolant through a secondinner tube positioned within the lumen; and cooling the first inner tubeand liquid coolant carried thereby with a gaseous coolant derived fromevaporation of liquid coolant released from the second inner tube andinto the lumen of the outer member.

In one or more embodiments, the flow of liquid coolant and the flow ofgaseous coolant are in different, e.g., opposite, directions.

In one or more embodiments, the outer member may be a heat exchangersheath. Further, outer members including tubes may include first andsecond tubes that are substantially parallel to each other such thatliquid coolant flows in substantially the same direction in through thefirst and second inner tubes, whereas gaseous coolant may flow in asecond, different direction through the lumen of the outer member tocool the first inner tube and liquid coolant carried thereby. Further,in one or more embodiments, an outer member of a hose may include anoutlet or port through which gaseous coolant derived from the liquidcoolant may flow out of the outer tube.

In one or more embodiments, an inner tube, such as the second tube,which does not deliver liquid coolant to a cryo-ablation device, mayextend through a substantial portion of the outer member, e.g., a distalend of the second inner member may terminated within the outer tube andbe adjacent to a distal end of the outer member, whereas an inner tube,such as the first inner tube, that delivers liquid coolant to thecryo-ablation device may extend completely through the outer member.

In one or more embodiments, the hose may include one or more additionalinner tubes, e.g., an inner tube coupled to an inter-balloon pressuresource or an inner tube to exhaust spent coolant from the cryo-ablationdevice.

In one or more embodiments, a hose or conduit or outer member may alsoinclude or be associated with a temperature sensor located within theouter member and a sensor associated with an inner tube to detectaccumulation of liquid coolant within the cryo-ablation device.

In one or more embodiments, gaseous coolant that is used to cool aninner tube that delivers liquid coolant to a cryo-ablation device may bederived from liquid coolant that flows through a different inner tubethat does not deliver liquid coolant to the cryo-ablation device.

In one or more embodiments, the liquid coolant may be liquid nitrousoxide, and the gaseous coolant may be gaseous nitrous oxide and othersuitable coolants such as gaseous CO₂, Argon and N₂.

In one or more embodiments, the cryo-ablation device may be a cryogeniccatheter, such as a cryogenic balloon catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout and in which:

FIG. 1 illustrates a cryo-ablation system constructed in accordance withone embodiment;

FIG. 2A illustrates a supply or extension hose or conduit apparatusconstructed according to one embodiment that may utilize internallygenerated gaseous coolant and counter flow chilling;

FIG. 2B illustrates a supply or extension hose or conduit apparatusconstructed according to another embodiment;

FIG. 3 illustrates a cryo-ablation system constructed in accordance withone embodiment that includes a cryogenic balloon catheter;

FIG. 4 illustrates an embodiment of a cryo-ablation system in which acatheter exhaust tube or lumen extends through the supply or extensionhose shown in FIG. 2A;

FIG. 5 illustrates another embodiment of a cryo-ablation system in whicha catheter exhaust tube or lumen does not extend through the supply orextension hose shown in FIG. 2A;

FIG. 6A illustrates a cryo-ablation system constructed according toanother embodiment;

FIG. 6B is a cross-sectional view of FIG. 6A along line B-B;

FIG. 6C is a cross-sectional view of FIG. 6A along lines C-C;

FIG. 6D is a cross-sectional view of FIG. 6A along line D-D;

FIG. 7A schematically illustrates a cryo-ablation system constructedaccording to a further alternative embodiment;

FIG. 7B is a cross-section view of FIG. 7A along line B-B; and

FIG. 7C is an enlarged view of a dispersion manifold shown in FIG. 7A.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

Embodiments relate to systems, apparatus and methods for cooling coolantto be provided to a cryo-ablation device, such as a cryogenic ballooncatheter, without the need for large, bulky consoles that are used inknown cooling systems, while addressing or improving upon issues ofcoolant warming, fluid resistance, and reduced coolant flow associatedwith known systems that use large consoles. Embodiments are able to coolor chill a liquid coolant that is to be provided to a cryo-ablationdevice at a location that is closer to the operation site and to alloweffective cooling at desired locations.

In one or more embodiments, a supply or extension hose or conduit forcooling or chilling liquid coolant that is to be delivered to acryo-ablation device includes an outer tube, member or sheath and two ormore inner conduits or tubes. At least one inner tube within the outermember carries liquid coolant to be delivered to the cryo-ablationdevice. A different inner tube within the outer member is of a certainlength or positioned such that it terminates within the lumen of theouter body and liquid coolant flowing through this inner tube vaporizesinto a gaseous coolant, which flows within the outer tube to cool orchill the at least one inner tube and liquid coolant carried therebythat is to be provided to the cryo-ablation device. Thus, embodimentsprovide “self-chilling” or “self-cooling” supply or extension hoses.

Further, in certain embodiments, gaseous coolant that cools or chillsthe inner tube and liquid coolant delivered to the ablation device flowsin a different direction than liquid coolant. Thus, self-chilling supplyor extension hoses may achieve chilling using “counter current” chillingor counter current heat exchange utilizing gaseous coolant that flows ina different direction than liquid coolant. For example, liquid coolantcan flow in one direction, e.g., towards the ablation device to which itis to be delivered, and gaseous coolant that cools the liquid coolantmay flow within the lumen in an opposite direction to be exhausted at anend of the supply hose that does not interface with the ablation device.This structural configuration provides for chilling of liquid coolant asthe liquid coolant flows within an inner tube to the ablation device,while exhausting the gaseous coolant at another end of the supply hose.Further aspects of various embodiments are described with reference toFIGS. 1-7C.

Referring to FIG. 1, a cryo-ablation system 100 constructed according toone embodiment includes a self-chilling supply or extension hose orconduit 110 (generally referred to as a supply hose 110), a proximal end111 of which is associated with, operably coupled to or connected to aninterface or small cryogenic console 120 (generally referred to asconsole 120), and a distal end 112 of which is associated with, operablycoupled to or connected to a proximal end 131 of a cryo-ablation device130. The distal end or tip 132 of the ablation device 130 is used tocryogenically ablate tissue including, but not limited to, cardiactissue, such as endocardial tissue, using cryogenic fluid 142 that issupplied from a tank or other reservoir 140. An inter-balloon pressuresource, pump, tube, lumen or line 150 is provided to control the exhaustpressure of the ablation device 130, and spent cryogenic fluids ormaterials are evacuated from the ablation device 130 through a catheterexhaust port, tube, lumen or line 160.

According to one embodiment, the cryogenic fluid 142 is a flowableliquid coolant at ambient temperature such as nitrous oxide (N₂O), andthe system 100 is configured to cryogenically ablate endocardial tissueto treat atrial fibrillation. It should be understood, however, thatembodiments may be implemented using other cryogenic refrigerants andfluids 142, and embodiments may be used in various other applications tocryogenically ablate different types of tissue in connection treatingother conditions and diseases. For ease of explanation, reference ismade to a cryogenic fluid or liquid coolant 142 generally, one exampleof which is nitrous oxide, which may be used with an ablation device tocryogenically ablate endocardial tissue to treat atrial fibrillation.

Referring to FIG. 2A, a self-chilling supply or extension hose 110constructed according to one embodiment includes an outer member or tube200 that includes or is formed of a sheath 202, e.g., thermallyinsulative or heat exchanger sheath, which defines an inner space orlumen 204 (generally referred to as lumen 204). The outer member 200 maybe made of materials having suitable flexibility, and the heat exchangersheath 202 may be made of, for example, high pressure reinforcedcryogenic tubing. The hose 110 may have a length of about 1 foot toabout 10 feet, e.g., about 6 feet and a width of about 0.125″ to about2″, e.g., about 0.5″. The hose 110 is coupled to the distal end 131 ofthe cryo-ablation device 130, which may have a length of about 1 foot toabout 6 feet, e.g., about 3 feet, and a diameter of about 0.05″ to about0.5″, e.g., about 0.1″.

With continuing reference to FIG. 2A, in the illustrated embodiment, theouter member 200 includes multiple inner tubes that are disposed orpositioned within the lumen 204. In the illustrated embodiment, thesupply hose 200 includes first and second inner tubes 220 a, 220 b, eachof which defines respective lumens 223 a, 223 b through which liquidcoolant 142 may flow, and each of which may, for example, be made of ahigh pressure cryogenic tubing with suitable heat transfer properties.The same source or tank 140 may supply liquid coolant 142 to both of theinner tubes 220 a, 220 b. Alternatively, different sources or tanks 140may supply liquid coolant 142 to the inner tubes 220 a, 220 b. In otherembodiments, different coolants 142 flow through the inner tubes 220 a,220 b. For ease of explanation, reference is made to a single supplytank 140 that provides coolant 142 to both of the inner tubes 220 a, 220b such that the same type of liquid coolant 142 flows through the lumens223 a, 223 b of both tubes 220 a, 220 b, but embodiments are not solimited.

The first inner tube 220 a, otherwise referred to as a catheter supplytube, is connected between, or in fluid communication with, the source140 of liquid coolant 142 and the cryo-ablation device 130. In oneembodiment, the first inner tube 220 a may have a length of about 1 footto about 10 feet, e.g., 6 feet, and a width of about 0.01″ to about0.25″, e.g., about 0.05″. Liquid coolant 142 that flows through thefirst inner tube 220 a is provided to the cryo-ablation device 130 forperforming cryogenic endocardial ablation. For example, a proximal end221 a of the first inner tube 220 a may be connected to a cryogenicfluid source 140 through the small console 120, and a distal end 222 aof the first inner tube 220 a may be connected to or interface with aproximal end 131 of the cryo-ablation device 130. An outer surface ofthe first inner tube 220 a may be sealed to the proximal and distal ends111, 112 of the outer member 200 in a fluid-tight manner.

In the embodiment illustrated in FIG. 2A, the first inner tube 220 aextends through the entire length of the supply hose 110 (through theproximal and distal ends 111, 112 of the supply hose 110) such thatneither the proximal end 221 a nor the distal end 222 a of the firstinner tube 220 a terminates within the supply hose 110, but embodimentsare not so limited.

In the embodiment illustrated in FIG. 2A, the second inner tube 220 b,otherwise referred to as a chilling coolant supply tube, does notdeliver liquid coolant 142 to the cryo-ablation device 130 as does thefirst inner tube 220 a. In one embodiment, the second inner tube 220 bmay have a length of about 1 foot to about 10 feet, e.g., about 6 feet,and a width of about 0.01″ to about 0.25″, e.g., about 0.05″. In theembodiment illustrated in FIG. 2A, the second inner tube 220 b does notextend across the entire length of the supply hose 110. Rather, in theillustrated embodiment, a proximal end 221 b of the second inner tube220 b may extend through and be sealed to the proximal end 111 of theouter member 200 in a fluid-tight manner and be in fluid communicationwith the fluid source 140 and console 120 (similar to the first innertube 220 a described above), but a distal end 222 b of the second innertube 220 b terminates within the lumen 204 of the outer member 200.Referring to FIG. 2B, in an alternative embodiment, the second innertube 220 b may be positioned outside of the outer member 200 and bearranged or connected such that the distal end 222 b of the second innertube 220 b terminates within the lumen 204 of the outer member 200.

Thus, as generally illustrated in FIGS. 2A-B, the second inner tube 220b may extend through a substantial portion of the outer member 200 (asshown in FIG. 2A) or through small portion of the outer member 200 (asshown in FIG. 2B). Further, FIGS. 2A-B illustrates that coolant 230released from the second inner tube 220 b may flow in differentdirections within the outer member 200 (as shown in FIG. 2A) or in asingle or substantially the same direction (as shown in FIG. 2B).

With these configurations and tube 220 a, 220 b arrangements, liquidcoolant 142 that flows through the lumen 223 b of the second inner tube220 b is released through a distal opening 224 b of the second innertube 220 b and into the lumen 204 of the outer member 200. The releasedcoolant 142 vaporizes into a gas 230 that flows inside of the outermember 200. The resulting gas 230 cools the first inner tube 220 a andthe liquid coolant 142 carried thereby. For example, the temperature ofthe high pressure liquid coolant may be cooled to near the temperatureof the saturation line at ambient temperature. For nitrous oxide, thisis about −80° C. Although these different embodiments may be utilizedand function in similar manners, reference is made to the apparatusconfiguration shown in FIG. 2A for ease of explanation.

More particularly, FIG. 2A generally illustrates gaseous coolant 230flowing along one side of the first inner tube 220 a, or along the topof the first inner tube 220 a in the embodiment illustrated in FIG. 2A.However, during use, gaseous coolant 230 may flow along or over variousother sides or surfaces of the first inner tube 220 a, e.g., around theentire first inner tube 220 a. Thus, FIG. 2A is provided to generallyillustrate flow of gaseous coolant 230 along the first inner tube 220 a.The second inner tube 221 a may have a spirally wrapped filament, tubeor other suitable structure (not shown in FIGS. 2A-B), which allows thegaseous coolant 230 to pass or flow next to the first inner tube 221 awhile preventing the first inner tube 221 a from touching the innersurface of the outer member 200, thus enhancing chilling effects andinsulation.

These counter current chilling or heat exchange configurations allowliquid coolant 142 to be chilled or cooled within the supply hose 110using internally generated gaseous coolant 230, thus providing aself-chilled supply hose 110. The chilled liquid coolant 142 that flowsthrough the first inner tube 220 a may then be delivered to thecryo-ablation device 130 at desired temperatures and pressures as aresult of being chilled by the internally generated gaseous coolant 230.For this purpose, it still may be necessary to use some type of console120, but not the large, bulky consoles of known systems. Further, withembodiments, it is not necessary for the console 120 to include anindependent chiller, compressor or pressurizing apparatus as in known,larger consoles. Thus, with embodiments, additional liquid coolant 142is utilized for self-chilling in order to reduce the footprint andcomponents of the console 120 such that significantly smaller consoles120, e.g., portable and disposable consoles 120 that do not includechillers, may be utilized instead, while also achieving lower coolant142 temperatures at the cryo-ablation device 130 for more effectivecryo-ablation of tissue.

In embodiment illustrated in FIG. 2A, self-chilling of the inner tube220 a and coolant 142 carried thereby is achieved utilizing countercurrent flows. More specifically, liquid coolant 142 flows insubstantially the same direction through the first and second innertubes 220 a, 220 b, but gaseous coolant 230 flows within the outermember 200 in a different direction to cool the first inner tube 220 aand liquid coolant 142 provided to the cryo-ablation device 130. In theillustrated embodiment, the first and second inner tubes 220 a. 220 bare substantially parallel to each other (although they may beconfigured in different manners), and liquid coolant 142 flows in afirst direction towards the distal end 112 of the supply tube 110 andthe ablation device 130, whereas in the illustrated embodiment, gaseouscoolant 230 flows in an opposite direction towards the proximal end 111of the supply tube 110 and is released through an exhaust port or tube240. Other embodiments may involve flow of liquid coolant 142 andgaseous coolant 230 that are in different directions, but notnecessarily opposite directions. Further, in the embodiment illustratedin FIG. 2A, the exhaust port or tube 240 is defined or extends throughthe proximal end 111 of the outer member 110, but other embodiments mayutilize an exhaust port 240 that is defined through a different sectionof the outer member 200 depending on, for example, the number andorientation of inner tubes 220 within the outer member 200.

Further, the degree of self-cooling utilizing counter current heatexchange or chilling can be adjusted by configuring the tubes 220 a, 220b in different positions or configurations, e.g., as shown in FIGS.2A-B. As a further example, in the illustrated embodiment, the distalend 222 b of the second inner tube 220 b is close to or adjacent to thedistal end or wall 112 of the outer member 200 such that gaseous coolant230 released by the second inner tube 220 b flows through a substantialportion of the outer tube lumen 204 and comes into contact with asubstantial portion of the outer surface of the first inner tube 220 a.If more cooling is desired, the second inner tube 220 b may bepositioned closer to the distal end 112 of the outer tube 110, closer tothe first inner tube 220 a. Further, larger quantities of liquid coolant142 may be provided through the second inner tube 220 b in order togenerate larger quantities of gaseous coolant 230 to enhance chilling.Moreover, the surface area of the first inner tube 220 a that is exposedto or in thermal contact with the gaseous coolant 230 may be increased.Additionally, the time during which the first inner tube 220 is exposedto or in thermal contact with the gaseous coolant 230 may be increased.Thus, embodiments can be adapted to satisfy different self-chilling orinternal cooling needs and different system and ablation device 130configurations.

Referring to FIG. 3, a system 300 constructed according to anotherembodiment includes a self-chilling supply hose 110 (e.g., as describedwith reference to FIGS. 1-2) and a cryo-ablation device 130 in the formof a cryogenic balloon catheter 300 that is coupled to or in fluidcommunication with the supply hose 110 via an interface 310. In theillustrated embodiment, the cryogenic balloon catheter 300 includes adilation-type cryogenic balloon tip that includes a balloon member 330.Further, in the illustrated embodiment, the interface 310 is in the formof a Y-adapter. A first portion 315 of the Y-adapter is coupled to thedistal end 112 of the supply hose 110, a second portion 316 of theY-adapter is coupled to a proximal end 131 of the cryo-ablation device130. In a third portion 317 of the Y-adapter, a guide wire lumen 320accommodates a guidewire 322 that may include a steerable or deflectabletip for facilitating insertion and positioning of the cryogenic ballooncatheter 300 within a patient.

With further reference to FIG. 4 (which omits the guide lumen 320 andwire 322 for ease of illustration), the console 120 may include one ormore valves 401 a, 401 b (generally 401) that may be utilized to controlthe delivery of liquid coolant 142 from the supply tank 140 to the innertubes 220 a, 220 b of the supply tube 110. In the illustratedembodiment, the first inner tube 220 a may be cooled by gaseous coolant230 by opening the valve 401 b so that liquid coolant 142 flows throughthe lumen 223 b of the second inner tube 220 b, and the valve 401 a maybe opened to allow the liquid coolant 142 chilled by the gaseous coolant230 to flow through the lumen 223 a of the first inner tube 220 a and bedelivered to the cryogenic balloon catheter 300. Although FIG. 4 showstwo valves 401 a, 401 b and a supply line 141 that is split into thefirst and second inner tubes 220 a, 220 b configuration, other valve andsupply line configurations may also be utilized to provide a liquidcoolant 142 to the supply hose 110.

Referring again to FIG. 3, in one embodiment, the exhaust tube or lumen160 for evacuating spent coolant from the cryogenic balloon catheterextends through the supply tube 110 and the console 120. In anotherembodiment, as shown in FIG. 4, the exhaust tube or lumen 160 extendsthrough the supply tube 110, but not the console 120. In a furtherembodiment, as shown in FIG. 5 (in which a guidewire lumen 320 andguidewire 322 are also omitted for clarity), the exhaust tube or lumen160 may extend from the interface 310, but not through the supply tube110 or the console 120. Thus, FIGS. 3-5 show that spent coolant can beevacuated from the cryo-ablation catheter 300 in different ways and mayextend through different system components. FIGS. 6A-7C illustratefurther embodiments of systems that include a self-chilling supply hose110 that utilizes internally generated gaseous coolant 230 that may flowthrough the supply hose 110 in a different direction than liquid coolant142 to cool or chill liquid coolant 142 before it is provided to acryo-ablation catheter 300.

Referring to FIGS. 6A-D, a system 600 constructed according to anotherembodiment includes a self-chilling supply or extension hose 110 and aninner sheath 610 disposed within a larger, outer sheath 620. In theillustrated embodiment, inter-balloon pressure and catheter exhausttubes or lines 150, 160 are enclosed within a sheath 610 that extendsthrough an outer sheath 620 that encloses the sheath 610 and the supplytube 110. The first inner tube 220 a (the catheter supply tube), thesecond inner tube 220 b (chilling coolant supply tube), the exhaust portor tube 240 to exhaust gaseous coolant 230, the inter-balloon pressuretube 150 and catheter exhaust tube 160 may be connected to a proximalconnector 631 to facilitate connection to or interfacing with theconsole 120 or another system component. One suitable proximal connector631 that may be used with embodiments is a latching connector.Similarly, a distal hose connector 632 is adapted to connect the firstinner tube 220 a (the catheter supply tube), the inter-balloon pressuretube 150 and the catheter exhaust tube 160 to the interface 310 suchthat these tubes are in fluid communication with the cryogenic ballooncatheter 300. Latching connectors may also be used for this purpose. Theproximal and distal hose connectors 631, 632 may also be advantageouslyconnected by a strain relief wire 633 to protect the connectors 631, 632from damage of disconnection if inadvertently pulled. During use, thefirst inner tube 220 a is cooled by gaseous coolant 230 derived fromliquid coolant 142 flowing through the second inner tube 220 b, andchilled liquid coolant 142 is provided by the first inner tube 220 a tothe cryogenic balloon catheter. As a result, the balloon member 330expands, and cardiac tissue adjacent to the balloon member 330 may becryogenically ablated. Spent coolant is evacuated from the cryogenicballoon catheter 300 through the exhaust port or tube 240.

FIGS. 7A-C illustrate another system 700 that includes a self-chillingsupply or extension hose 110 and how other system components can beoperably connected to perform cryo-ablation. In the illustratedembodiment, the first inner tube 220 a may extend into the catheter 300,or be connected to or in fluid communication with a separate cathetersupply tube or lumen 720 that extends through the body 302 of thecryogenic balloon catheter 300, such that at least one tube or lumen,whether the first inner tube 220 a or the internal catheter supply tubeor lumen 720, supplies previously chilled liquid coolant 142.

In the illustrated embodiment, a distal end of the elongate body 302 orextrusion, includes a dispersion member or manifold 710, which is usedto distribute coolant. The dispersion member 710 extends from theelongate body 302 and defines an internal lumen or space 712 that is influid communication with a distal end or outlet of the catheter supplytube 720. In the illustrated embodiment, the dispersion member 710includes dispersion elements 712 that are sealingly engaged orconnected, e.g., welded 713, to the elongate body 302 to define nozzlesor apertures 714 through which coolant is distributed. The outlet 782 oftubular element 781 is blocked or sealed. For example, during assemblyof the manifold 710, the seals can be welded 713, and a gas may be blownthrough tubular element 781 to clear out particles, and then the tubularelement 781 may be sealed 782. This prevents or reduces particlesblocking nozzles 714.

In the illustrated embodiment, the balloon 330 includes an outer wall741 that surrounds or encloses an inner wall 742 to define anintermediate space 743 between the balloon outer and inner walls 741,742. The balloon 330 also defines an internal chamber 730 defined by aninner surface of the inner wall 742. The outlet of the supply tube orlumen 720 through which pre-chilled liquid coolant 142 flows is in fluidcommunication with the internal space 712 of the dispersion member 710and the internal chamber 730. The catheter exhaust tube or lumen 160, oranother tube or lumen 722 that extends through the elongate body 302, isin fluid communication with the internal chamber 730. The inter-balloonpressure tube or lumen 150, or a separate tube or lumen 724 that extendsthrough the body 302, is in fluid communication with the intermediatespace 743 defined between the walls 741, 742 of the balloon 370.

During use, liquid coolant 142 is provided to the supply hose 110 fromthe supply tank 140 by opening one or more valves 750 a-c. The liquidcoolant 142 may flow through a supply line 141, which may divided orsplit into two separate inner lines or tubes 220 a, 220 b (as shown inFIG. 4). In the illustrated embodiment, liquid coolant 142 flowingthrough the first inner tube 220 at is chilled by counter-flowinggaseous coolant 230. One or more temperature sensors or thermocouples760 a, 760 b (generally referred to as temperature sensor 760) may beutilized to monitor the effect of chilling of the liquid coolant 142within the supply hose 110, e.g., by use of a controller,microprocessor, or other suitable hardware and software, generallyidentified as 770 in FIG. 7A. Chilled liquid coolant 142 flows throughthe first inner tube 220 a and the catheter supply tube or lumen 720 aand is released into the internal space 712 of the dispersion member710.

Due to the resulting pressure drop resulting from chilled liquid coolant142 being released into the space 712, the chilled liquid coolant 142 ischilled into a spray of very cold liquid and gas. The pressure of theliquid coolant 142 and supply line 720 dimensions are such that the verycold, partially liquid coolant 142 sprays against an inner surface ofthe inner balloon wall 742, absorbs heat, and evaporates rapidly,thereby causing the expandable balloon 742 to inflate. During ablation,the walls of the balloons 741, 742 are pressed together and press on thetissue to be ablated. Cryo-ablation is accomplished by the resultingrapid cooling of the balloon walls 741, 742 while the outer balloon wall741 is positioned against or within cardiac tissue that is beingablated.

Spent gaseous coolant is then evacuated through the tube or lumen 722and the outlet port or tube 150. The flow and pressure of the spentgaseous coolant exhausted from the catheter 300 may be monitored with acoolant flow sensor 764, a pressure sensor 766 or other suitabledevices. Further, one or more flood sensors 762 a, 762 b may bepositioned within the catheter exhaust lumen 160 and/or theinter-balloon pressure lumen 150 to monitor the presence of electricallyconductive liquids (e.g., blood) within the catheter 300 in order todetermine whether the inter-balloon pressure level should be adjusted orthe coolant flow should be stopped, e.g., using the controller 770 orother suitable components.

Although particular embodiments have been shown and described, it shouldbe understood that the above discussion is not intended to limit thescope of these embodiments. Various changes and modifications may bemade without departing from the scope of the claims. For example,embodiments may be configured to perform ablation of various types oftissue for treatment of different conditions or diseases, one example ofwhich is to perform endocardial ablation to treat atrial fibrillation asdescribed above. Other embodiments may be implemented to cool or chillliquid coolants provided to cryo-ablation devices that are components ofopen-loop, or closed-loop, fluid-fed catheter systems.

Moreover, although embodiments are described herein with reference to aself-chilling supply hose that utilizes internally generated gaseousnitrous oxide to cool or chill liquid nitrous oxide, in otherembodiments, gaseous nitrous oxide may be used to chill or cooldifferent types of liquid coolants and refrigerants, and that thegaseous coolant may be a gaseous coolant other than gaseous nitrousoxide. Further, coolants as described herein may, in certainembodiments, and depending on the coolant used, be a flowable mixture ofa gas and a liquid. Thus, although a coolant may be a “liquid” or haveliquid-like properties, the coolant may be a flowable or fluid mixtureof a liquid and a small amount of gas. Further, the coolant carried bythe second inner tube that is utilized to cool or chill coolant that iscarried by the first inner tube and to the cryo-ablation device may bethe same type of coolant or different types of coolants, and may be thesame phase (e.g., a liquid) or different phases.

Embodiments may also be implemented utilizing a supply hose individually(which may be disposable), or as a combination of a supply hose andcatheter (the combination of which may also be disposable), and ascombinations of other system components described above.

Thus, embodiments are intended to cover alternatives, modifications, andequivalents that may fall within the scope of the claims.

What is claimed is:
 1. A method of supplying cooled liquid coolant to acryo-ablation device, comprising: delivering liquid coolant through afirst inner tube extending through a lumen defined by an outer membercoupled to the ablation device, the first inner tube in fluidcommunication with an interior of the ablation device; delivering liquidcoolant through a second inner tube at least partially positioned withinthe outer member lumen; and cooling the first inner tube and liquidcoolant carried therein with a gaseous coolant derived from evaporationof liquid coolant released from the second inner tube and into the outermember lumen.
 2. The method of claim 1, the first and second inner tubesbeing configured and arranged such that liquid coolant flows through thefirst inner tube in a first direction, and gaseous coolant flows in theouter member lumen in a second direction different than the firstdirection.
 3. The method of claim 2, wherein the first direction and thesecond direction are opposite directions.
 4. The method of claim 1,further comprising exhausting the gaseous coolant through an outletdefined by the outer member lumen.
 5. The method of claim 1, wherein thefirst inner tube is not in fluid communication with the second innertube or the outer member lumen.
 6. The method of claim 1, furthercomprising monitoring an effect of the cooling the first inner tube andliquid coolant carried therein by monitoring a temperature of the firstinner tube and liquid coolant carried therein within the outer memberlumen.
 7. The method of claim 1, further comprising exhausting spentcoolant from the ablation device through a third tube extending throughthe outer member lumen.
 8. The method of claim 7, further comprisingmonitoring a pressure of the spent coolant exhausting from the ablationdevice.
 9. The method of claim 7, further comprising monitoring a flowrate of the spent coolant exhausting from the ablation device.